Myocardial infarction and short- or long-term risk of a subsequent cancer diagnosis: a Danish Nationwide Cohort Study

Background: Growing evidence suggests that myocardial infarction (MI) may be a marker of cancer risk, but many aspects of this relation are poorly understood. Objectives: To examine the short- and long-term risk of incident cancer in patients presenting with MI. Methods: Using nationwide population-based Danish health registries, we identified all patients with a first-time diagnosis of MI (1995-2021) and followed them for up to 28 years for any subsequent diagnosis of cancer. We computed risks and standardized incidence ratios with 95% CIs as the observed number of cancers relative to the expected number based on national cancer incidence rates by sex, age, and calendar year. Results: Among 185 065 patients diagnosed with MI, we observed 25 315 subsequent cancers. The risk of any cancer was 2.4% after 1 year of follow-up, increasing to 25.8% after 28 years, taking the competing risks of death into account. During the first year of follow-up, the standardized incidence ratio of any cancer was 1.67 (95% CI, 1.62-1.73). The standardized incidence ratio remained moderately elevated during 2 to 5 years (1.03; 95% CI, 1.01-1.05) and beyond 5 years (1.07; 95% CI, 1.05-1.09). The strongest associations were found for hematological as well as obesity- and smoking-related cancers during the first year of follow-up, whereas primarily, the risk of smoking- related cancers remained elevated throughout the entire follow-up period. Conclusion: MI was associated with subsequent risk of cancer, driven by hematologic, obesity-, and smoking-related cancers in the short term and smoking-related cancers in the long term.